The present invention relates to functionalized polymers, compositions containing the same, articles prepared from the same, and methods for producing the same. In particular, the invention provides the radical melt functionalization(s) of polyolefins, such as propylene-based polymers, using certain coagents. Such functionalization processes result in functionalized polymers with enhanced molecular weights, as compared to the functionalized polymers formed from melt functionalization reactions in the absence of the coagents.